# Notes And Questions NCERT Class 12 Physics Chapter 6 Electromagnetic Induction

Please refer to Electromagnetic Induction Class 12 Physics Notes and important questions below. The Class 12 Physics Chapter wise notes have been prepared based on the latest syllabus issued for the current academic year by CBSE. Students should revise these notes and go through important Class 12 Physics examination questions given below to obtain better marks in exams

## Electromagnetic Induction Class 12 Physics Notes and Questions

The below Class 12 Electromagnetic Induction notes have been designed by expert Physics teachers. These will help you a lot to understand all the important topics given in your NCERT Class 12 Physics textbook. Refer to Chapter 6 Electromagnetic Induction Notes below which have been designed as per the latest syllabus issued by CBSE and will be very useful for upcoming examinations to help clear your concepts and get better marks in examinations.

• Magnetic Flux:
Magnetic flux through a plane of area dA placed in a uniform magnetic field B

This is because magnetic lines of force are closed lines and free magnetic poles do not exist.

a) First Law: whenever there is a change in the magnetic flux linked with a circuit with time, an induced emf is produced in the circuit which lasts as long as the change in magnetic flux continues.
b) Second Law: According to this law,

• Lenz’s Law:
The direction of the induced emf or current in the circuit is such that it opposes the cause due to which it is produced, so that,

Where N is the number of turns in coil
Lenz’s law is based on energy conservation.

• Induced BMF and Induced Current:
a) Induced EMF,

Charge depends only on net change in flux does not depends on time.

• Induced Emf due to Linear Motion of a Conducting Rod in a Uniform Magnetic Field
The induced emf,

• Induced EMF due to Rotation of a Conducting Rod in a Uniform Magnetic Field:
The induced emf,

Where n is the frequency of rotation of the conducting rod.

• Induced EMF due to Rotation of a Metallic Disc in a Uniform Magnetic Field:

• Induced EMF, Current and Energy Conservation in a Rectangular Loop Moving in a Non- Uniform Magnetic Field with a Constant Velocity:
a) The net increase in flux crossing through the coil in time ..1t is,
△ø = (b2 – b2) lv△r
b) Induced emf in the coil is,
E = (b2 – b2) lv

Energy supplied in this process appears in the form of heat energy in the circuit

f) Energy supplied due to flow of current I in time ..△t is,

• Rotation of Rectangular Coil in a Uniform Magnetic Field:
a) Magnetic flux linked with coil
ø = BAN cos ø
=BAN cosøλ
b) Induced emf in the coil

c)  Induced current in the coil.

d) Both Emf and current induced in the coil are alternating

• Self-Induction and Self Inductance:
a) The phenomenon in which an induced emf is produced by changing the current in a coil is called self in induction

where L is a constant, called self inductance or coefficient of self- induction.
b) Self inductance of a circular coil

c)  Self inductance of a solenoid

d) Two coils of self- inductances L1and Lz. placed far away (i.e., without coupling) from each other.
i) For series combination:
L = L1 + L2…………..Ln
ii) For parallel combination

• Mutual Induction and Mutual Inductance:
a) On changing the current in one coil, if the magnetic flux linked with a second coil changes and induced emf is produced in that coil, then this phenomenon is called mutual induction

Therefore, M12 = M21 = M
b) Mutual inductance two coaxial solenoids

c)  If two coils of self- inductance L1 and L2 are wound over each other, the mutual inductance is,

Where K is called coupling constant
d) Mutual inductance for two coils wound in same direction and connected in series
L = L1 + L2 + 2M
e) Mutual inductance for two coils wound in opposite direction and connected in series
L = L1 + L2 – 2
f) Mutual inductance for two coils in parallel

• Eddy Current:
When a conductor is moved in a magnetic field, induced currents are generated in the whole volume of the conductor. These currents are called eddy currents.

• Transformer:
a) It is a device which changes the magnitude of alternating voltage or current.

• Generator or Dynamo:
It is a device by which mechanical energy is converted into electrical energy. It is based on the principle of electromagnetic induction.

• Different Types of Generator:
a) AC Generator
It consists of field magnet, armature, slip rings and brushes. b) DC Generator
It consists of field magnet, armature, commutator and brushes.

• Motor:
It is a device which converts electrical energy into mechanical energy. Back emf e ∝φ Current flowing in the coil,

Where R is the resistance of the coil. Out put Power = iq eb Efficiency,